feat(readiness): add W1-T semantic timing proxy

docs(aligners): finalize three-backend selection

fix(nemo): close empirical alignment validation

chore(repo): finalize licensing and documentation

docs(aligners): finalize Stage 5 acceptance

feat(whisperx): add reference-text alignment backend

feat(mfa): add forced alignment backend

feat(nemo): add forced alignment backend

feat(aligners): add backend-neutral alignment framework

docs(aligners): freeze Stage 0 architecture and tooling